1. Field of the Invention
The invention relates to containers with dual locking configurations, which can be used to securely latch a lid to a tray before and after one or both experience a size change. One application relates to plastic containers, which experience thermal shrinkage during the baking of food.
2. Description of the Related Art
Containers having a tray portion and a lid portion come secured to each other to protect the contents of the container from outside elements and or to prevent spillage of the contents. If the tray, the lid, or both expand or contract due to thermally induced dimensional changes, temperature changes, load stresses, or other interactions, the lid will no longer fit on the tray. It is desired that the container lid still fit on the tray both before and after one or both change size.
Plastic baking trays shrink in the oven during baking, as a result, prior art lids have been designed to fit the tray either before or after baking but not both before and after baking.
It is desirable to have tray lids that will attach to the tray both before and after the tray changes sizes due to thermally induced shrinkage. The tray lid should be securely locked onto the tray such that a good seal is maintained to protect the food therein.
In other applications a tray may have a first size before it is filled and a second size after it is filled. It is desirable to have tray lids that will attach to the tray both before and after the tray changes sizes due to stresses applied to or removed from the tray.
A container having a tray with a lid attached thereto is provided wherein the tray, the lid or both have two sets of engagement mechanisms in different locations, such that when the tray or lid is a first size a first set of engagement mechanisms are employed and when the tray and or lid is a second size a second set of engagement mechanisms are employed to secure the lid to the tray.
For example plastic trays are well suited for baking a variety of food products. However, one problem with such trays is that they shrink when subjected to heat at typical baking temperatures. In the past, separate covers would have to be provided to keep the food fresh. One cover would be used before baking and one after baking. The use of two covers substantially increases the cost of packaging and can lead to a level of inconvenience and dissatisfaction on the part of consumers.
The present invention solves these problems by providing a tray and a single lid to cover the food both before and after baking to keep the food fresh. A feature of the invention is to provide a tray and a lid arrangement with dual sets of closure elements, one set used before thermal shrinkage has occurred and the other used after the tray has experienced thermal shrinkage.
In one embodiment, the two sets of closure elements are provided on the lid so that one set fits and seals with the tray before baking and the other set fits and seals with the tray after thermal shrinking has occurred.
In another embodiment, the two sets of closure elements are provided on the tray and cooperate with members on the lid.
The invention can be used in conjunction with any of a variety of tray and lid designs and with trays and lids made of a variety of different plastic materials. Those skilled in the art can use well known techniques to measure or calculate shrinkage and then use the invention to produce products that require only a single cover.
It is an object of the invention to provide one lid that fits a tray of a first size before baking and also fits the same tray after it thermally shrinks to a second size due to baking.
It is an object of the invention to seal plastic baking trays with a single lid before and after baking food in the tray.
It is an object of the invention to provide a lid which is easy to open and close at two tray sizes.
It is an object of the invention to provide a lid with two sizes of engagement perimeters one for the size of the tray before baking and one for the size of the tray after baking.
It is an object of the invention to provide a tray with two sizes of engagement perimeters one for engaging the lid before baking and one for engaging the lid after baking.
It is an object of the invention to provide lids, which fit trays, subjected to thermal shrinkage.
It is an object of the invention to provide lids, which fit trays, subjected to thermal expansion.
It is an object of the invention to provide trays, which fit lids, subjected to thermal shrinkage.
It is an object of the invention to provide trays, which fit lids, subjected to thermal expansion.
It is an object of the invention to provide trays, which fit lids, subjected to stress shrinkage.
It is an object of the invention to provide trays, which fit lids, subjected to stress expansion.
It is an object of the invention to provide lids, which fit trays, subjected to stress shrinkage.
It is an object of the invention to provide lids, which fit trays, subjected to stress expansion.
Other objects, advantages and novel features of the present invention will become apparent from the following detailed description of the invention when considered in conjunction with the accompanying drawing.